Hydraulic Flaring Tool Kit for Transmission Cooler Lines

A hydraulic flaring head is the difference between a cooler line that seals on the first try and one you fight with for an hour. This kit uses a hand-pumped hydraulic ram instead of a screw yoke, so the die pushes the flare square with even pressure. That matters most on the hard steel cooler lines running from a 4L60E, 4L80E, 6L80 or 68RFE case up to the radiator cooler, where a lopsided flare will weep ATF at the fitting no matter how hard you torque it.

The die set covers the sizes a transmission shop actually runs into: dedicated transmission cooling dies in 3/8 in and 1/2 in, 45-degree SAE inverted flare dies from 3/16 in through 1/2 in, ISO bubble flare dies in 4.75 mm through 10 mm for import and late-model domestic lines, GM fuel line dies in 5/16 in and 3/8 in, and push-connect dies in 1/4 in through 3/8 in. Sixteen dies and seventeen adapters ship in the case, along with grease, five sealing rings and a pair of gloves.

On the bench the sequence is short: cut the tube with the included cutter (it handles 1/8 in through 5/8 in), deburr the ID and OD with the supplied deburring tool, grease the die face, clamp the tube in the yoke at the marked depth, and pump the ram until the die bottoms. For a double flare, run the first-stage die, back the ram off, then finish with the second-stage die. The yoke is 42CrMo steel, which is what keeps it from spreading after a few hundred flares.

One limit worth knowing up front: this tool is rated for copper, copper-nickel, aluminum and mild steel tubing. It is not for stainless steel lines. If you are replacing a rusted-out cooler line with stainless, you need a stainless-rated flaring tool instead.